Heart attacks are caused by the blood supply to the heart being suddenly interrupted. Without this supply, heart muscles may be damaged and begin to die.

Without treatment, the heart muscles will experience irreversible damage.

If a large portion of the heart is damaged in this way, the heart stops beating (known as a cardiac arrest), resulting in death.

Coronary heart disease

Coronary heart disease (CHD) is the leading cause of heart attacks. CHD is a condition in which the coronary arteries (the major blood vessels that supply the heart with blood) get clogged up with deposits of cholesterol. These deposits are called plaques.

Before a heart attack, one of the plaques ruptures (bursts), causing a blood clot to develop at the site of the rupture. The clot may block the supply of blood to the heart, triggering a heart attack.